CN117897631A - Light emitting element driving circuit, active sensor, and object recognition system - Google Patents
Light emitting element driving circuit, active sensor, and object recognition system Download PDFInfo
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- CN117897631A CN117897631A CN202280058792.0A CN202280058792A CN117897631A CN 117897631 A CN117897631 A CN 117897631A CN 202280058792 A CN202280058792 A CN 202280058792A CN 117897631 A CN117897631 A CN 117897631A
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- 239000004065 semiconductor Substances 0.000 claims abstract description 18
- 238000005286 illumination Methods 0.000 claims description 23
- 239000003990 capacitor Substances 0.000 claims description 13
- 239000011324 bead Substances 0.000 claims description 7
- 229910000859 α-Fe Inorganic materials 0.000 claims description 7
- 230000005669 field effect Effects 0.000 claims description 6
- 230000001678 irradiating effect Effects 0.000 claims 1
- 230000003287 optical effect Effects 0.000 abstract description 5
- 238000010586 diagram Methods 0.000 description 33
- 238000000034 method Methods 0.000 description 28
- 230000000052 comparative effect Effects 0.000 description 15
- 230000003071 parasitic effect Effects 0.000 description 8
- 230000004048 modification Effects 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- 230000008569 process Effects 0.000 description 5
- 238000001514 detection method Methods 0.000 description 4
- 238000004088 simulation Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 238000004422 calculation algorithm Methods 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000013527 convolutional neural network Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000005401 electroluminescence Methods 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000011176 pooling Methods 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 239000000470 constituent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000009499 grossing Methods 0.000 description 1
- 238000010801 machine learning Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/484—Transmitters
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/32—Pulse-control circuits
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
- H05B45/3725—Switched mode power supply [SMPS]
- H05B45/375—Switched mode power supply [SMPS] using buck topology
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
- H05B45/3725—Switched mode power supply [SMPS]
- H05B45/38—Switched mode power supply [SMPS] using boost topology
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
- H05B47/10—Controlling the light source
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Electromagnetism (AREA)
- Computer Networks & Wireless Communication (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Led Devices (AREA)
Abstract
An input voltage (V) for supplying a DC to the input terminal (IN) H ) Output terminal (OUT) and semiconductor deviceThe optical elements (402) are connected. The half-bridge circuit (510) includes a high-side transistor (MH) disposed between the input terminal (IN) and the switch node (SW) and a low-side transistor (ML) disposed between the switch node (SW) and the ground terminal (GND). The control circuit (530) turns on both the high-side transistor (MH) and the low-side transistor (ML) in the period (T1) of the 1 st period and turns on only the high-side transistor (MH) in the period (T2) of the following 2 nd period in accordance with a light emission command (S1) of the semiconductor light emitting element (402).
Description
Technical Field
The present disclosure relates to a driving circuit of a light emitting element.
Background
For automatic driving or automatic control of the light distribution of a headlight, an object recognition system that senses the position and type of an object existing around a vehicle is used. The object recognition system includes a sensor and an arithmetic processing device that analyzes an output of the sensor. The sensor is selected from cameras, liDAR (Light Detection and Ranging: light detection and ranging, laser Imaging Detection and Ranging: laser imaging detection and ranging), millimeter wave radar, ultrasonic sonar, etc., in view of the application, required accuracy, and cost.
The sensor includes a passive sensor and an active sensor. The passive sensor detects light emitted from an object or light obtained by reflecting ambient light from the object, and the sensor itself does not emit light. On the other hand, an active sensor irradiates illumination light to an object and detects reflected light thereof. Active sensors mainly include a projector (illumination) that irradiates illumination light to an object and a photosensor that detects reflected light from the object. Active sensors have the following advantages: by matching the wavelength of the illumination light with the sensitivity wavelength region of the sensor, the resistance against disturbance can be improved as compared with a passive sensor.
[ Prior Art literature ]
[ patent literature ]
Patent document 1: japanese patent laid-open No. 2009-257983
Patent document 2: international publication WO2017/110413A1
Patent document 3: japanese patent laid-open publication No. 2019-68528
Disclosure of Invention
[ problem to be solved by the invention ]
LiDAR, toF cameras, and gating cameras as active sensors irradiate pulsed illumination light (pulsed illumination light) to a field of view. In order to improve the resolution of the distance, it is necessary to narrow the pulse width of the pulsed illumination light. In the circuit described in patent document 3, it is difficult to generate a relatively thin pulse current having a pulse width of about several ns (e.g., 2 ns).
In addition, if the pulse width is narrowed to a certain extent, the influence of parasitic inductance of the driving circuit cannot be ignored, the slew rate of the driving current decreases, and waveform passivation becomes remarkable.
One aspect of the present disclosure is accomplished under such a situation, and one of exemplary objects thereof is to provide a driving circuit capable of generating a pulse current of several ns. In addition, another exemplary object thereof is to provide a driving circuit that improves the slew rate of the driving current.
[ solution for solving the technical problem ]
One aspect of the present disclosure relates to a driving circuit of a semiconductor light emitting element. The driving circuit includes: an input terminal for receiving a DC input voltage; an output terminal connected to the semiconductor light emitting element; a half-bridge circuit including a high-side transistor and a low-side transistor, the high-side transistor being disposed between a switching node connected to the output terminal and the input terminal, the low-side transistor being disposed between the switching node and the ground terminal; and a control circuit that turns on both the high-side transistor and the low-side transistor in a period 1 according to a light emission instruction of the semiconductor light emitting element, and turns on the high-side transistor and turns off the low-side transistor in a period 2.
The above-described components are arbitrarily combined, and the components and the expression are replaced by each other in the method, the apparatus, the system, and the like, and are also effective as the present invention or the present disclosure. Further, the description of the item (means for solving the technical problem) does not describe all the features essential to the present invention, and therefore, a sub-combination of the described features may also be regarded as the present invention.
[ Effect of the invention ]
According to the present disclosure, a pulse current of several ns can be generated. In addition, the slew rate of the drive current can be improved.
Drawings
Fig. 1 is a circuit diagram of a light emitting device 400 according to an embodiment.
Fig. 2 (a) and (b) are equivalent circuit diagrams showing current paths of the driving circuit 500 in the 1 st period T1 and the 2 nd period T2 of the driving circuit of fig. 1.
Fig. 3 is an operation waveform diagram of the driving circuit 500 of fig. 1.
Fig. 4 is a circuit diagram of a calculation circuit model of the driving circuit used in the simulation.
Fig. 5 (a) is a waveform diagram of a control signal of the driving circuit of the embodiment, and fig. 5 (b) is a waveform diagram of a control signal of the driving circuit of the comparative technique 1.
Fig. 6 (a) and (b) are waveform diagrams showing voltages and currents generated at a plurality of nodes of the driving circuit according to the embodiment.
FIG. 7 shows the driving current I according to the embodiment DRV And comparing the drive current I of technique 1 DRV Is a waveform diagram of (a).
FIG. 8 shows the driving current I according to the embodiment DRV1 (solid line) and comparative technique 1 DRV2 (dotted line) drive current I of comparative technique 2 DRV3 Waveform diagram (one-dot chain line).
FIG. 9 (a) shows the coil current I L1 ～I L3 And drive current I DRV Fig. 9 (b) is a diagram showing the dependence of the short-circuit time T2 on the length of the driving voltage V DRV A graph of the dependence on the length of the short-circuit time T2.
Fig. 10 is a circuit diagram of a part of the driving circuit of modification 1.
Fig. 11 is a block diagram of an active sensor of an embodiment.
FIG. 12 is a block diagram of a gating camera of an embodiment.
Fig. 13 is a diagram illustrating an operation of the gating camera of fig. 12.
Fig. 14 (a) and (b) are diagrams illustrating images obtained by gating a camera.
Fig. 15 is a view showing a vehicle lamp incorporating an active sensor.
Fig. 16 is a block diagram showing a vehicle lamp including an object recognition system.
Detailed Description
(summary of the embodiments)
A summary of several exemplary embodiments of the disclosure is illustrated. This summary is provided to facilitate an understanding of some of the principles of one or more embodiments and is not intended to limit the breadth of the disclosure or the invention as described in the detailed description below. This summary is not an extensive overview of all contemplated embodiments, and is intended to neither identify key or critical elements of all embodiments nor delineate the scope of any or all aspects. For convenience, "one embodiment" may be used as an instruction to one embodiment (examples, modifications) or a plurality of embodiments (examples, modifications) disclosed in the present specification.
The driving circuit of the semiconductor light emitting element according to one embodiment includes: an input terminal for receiving a DC input voltage; an output terminal connected to the semiconductor light emitting element; a half-bridge circuit including a high-side transistor and a low-side transistor, the high-side transistor being disposed between a switching node connected to the output terminal and the input terminal, the low-side transistor being disposed between the switching node and the ground terminal; and a control circuit that turns on both the high-side transistor and the low-side transistor in a period 1 according to a light emission instruction of the semiconductor light emitting element, and turns on the high-side transistor and turns off the low-side transistor in a period 2.
During the 1 st period when both the high-side transistor and the low-side transistor are on, energy is stored in a minute inductance component included in the bridge circuit. Then, the low-side transistor is turned off to shift to the second period, and the driving voltage applied to the semiconductor light emitting element rises abruptly. Thus, a driving current having a steep slope can be supplied to the semiconductor light emitting element.
According to this configuration, a narrow pulse current having a pulse width of several ns (for example, 2 ns) can be generated. In addition, the voltage level of the input voltage required to generate a certain peak current can be greatly reduced as compared with other modes.
In one embodiment, the withstand voltage of the high-side transistor and the low-side transistor may be 2.5 times or more the input voltage.
In one embodiment, the high-side and low-side transistors may also be GaN-FETs (Field-Effect Transistor: field effect transistors).
In one embodiment, the length of the wiring pattern from the input terminal to the switching node via the high-side transistor may be longer than 100 μm. In one embodiment, the length of the wiring pattern extending from the ground terminal to the switching node via the low-side transistor may be longer than 100 μm. Thus, an optimum parasitic inductance can be introduced through the wiring pattern.
In an embodiment, the driving circuit may further include a Ferrite Bead (Ferrite Bead) provided between an output node of the power supply circuit generating the input voltage and the high-side transistor. In one embodiment, the drive circuit may also further include a feed-through capacitor connected to the input terminal. Thus, noise leaking from the bridge circuit to the power supply circuit can be reduced.
In an embodiment, the control circuit may turn off the high-side transistor and the low-side transistor during a period of a 3 rd period after the 2 nd period.
An active sensor of an embodiment includes: a light emitting device for emitting pulsed illumination light to a field of view; and a photosensor that receives reflected light of the pulsed illumination light from the field of view. The light emitting device may also include: a semiconductor light emitting element; and any one of the above driving circuits for driving the semiconductor light emitting element.
(embodiment)
Hereinafter, preferred embodiments will be described with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repetitive description thereof will be omitted as appropriate. In addition, the embodiments are not limited to the disclosure and the invention but are exemplified, and not all the features and combinations of the features described in the embodiments are essential to the disclosure and the invention.
Fig. 1 is a circuit diagram of a light emitting device 400 according to an embodiment. The light emitting device 400 generates illumination light of a narrow pulse having a pulse width in the order of nanoseconds. The light emitting device 400 includes a semiconductor light emitting element (hereinafter, simply referred to as a light emitting element) 402, a power supply circuit 404, a controller 406, and a driver circuit 500.
The light-emitting element 402 is an LD (laser diode), an LED (light-emitting diode), an organic EL (Electro Luminescence: electroluminescence) element, or the like.
The power supply circuit 404 generates a dc input voltage V H . Input voltage V H Is supplied to an input terminal IN of the driving circuit 500. For example, the power supply circuit 404 may be a switching power supply such as a boost converter, a buck-boost converter, a buck converter, or a charge pump circuit.
The controller 406 generates a timing signal indicating the light emission timing, that is, a light emission instruction S1, and supplies it to the control terminal CTRL of the driving circuit 500.
An output terminal OUT of the driving circuit 500 is connected to an anode of the light emitting element 402. The driving circuit 500 supplies a driving current I having a pulse width in the order of nanoseconds to the light emitting element 402 in response to the assertion of the light emission instruction S1 DRV 。
The driving circuit 500 includes a half-bridge circuit 510, pre-drivers 520H, 520L, and a control circuit 530. The half-bridge circuit 510 includes a high-side transistor MH and a low-side transistor ML. The high-side transistor MH is provided between the input terminal IN and the switching node SW connected to the output terminal OUT. The low-side transistor ML is provided between the switch node SW and the ground terminal GND. The switching node SW is connected to the output terminal OUT.
In order to realize a pulse width of several ns, the high-side transistor MH and the low-side transistor ML need to be switched at high speed. Therefore, as the high-side transistor MH and the low-side transistor ML, transistors excellent in high-frequency characteristics, such as GaN-FETs (Field-Effect Transistor: field effect transistors), can be used.
Half-bridge circuit 510 includes inductors L1-L3. The inductor L1 represents an inductance component between the input terminal IN and the switching node SW IN series with the high-side transistor MH. The inductor L2 represents an inductance component between the switching node SW and the ground terminal GND, which is connected in series with the low-side transistor ML. Inductor L3 represents an inductance component between switching node SW and the cathode of light emitting element 402.
The inductors L1 to L3 are parasitic inductances of pattern wirings, vias, wires, and the like on the printed substrate. As will be described later, the parasitic inductance is a predetermined short-circuit current I SHORT The magnetic energy stored in the inductors L1 and L2 is a critical parameter, and is preferably in the range of 0.1nH to 0.5 nH.
The parasitic inductance is preferably designed and adjusted, and from this point of view, it is preferable to use a pattern wiring on the printed board. That is, the inductor L1 is formed by a wiring pattern on a printed board on which the high-side transistor MH is mounted, and the parasitic inductance of the wiring pattern may be larger than 0.1 nH. The wiring length of the wiring pattern may be longer than 100 μm, for example. The wiring length of the wiring pattern is the length of a portion other than the pad to which the terminal portion of the high-side transistor MH is soldered.
Similarly, the inductor L2 is formed by a wiring pattern on the printed board on which the low-side transistor ML is mounted, and the parasitic inductance of the wiring pattern may be larger than 0.1 nH. The wiring length of the wiring pattern may be longer than 100 μm, for example. The wiring length of the wiring pattern is the length of a portion other than the pad to which the terminal portion of the low-side transistor ML is soldered.
The control circuit 530 generates the control signals HG and LG according to the light emission instruction S1 such that during the 1 st period T1, both the high-side transistor MH and the low-side transistor ML are turned on, and during the following 2 nd period T2, only the high-side transistor MH is turned on. The 1 st period T1 is also referred to as a short-circuit time, and the 2 nd period T2 is referred to as a light-emitting period.
The pre-drivers 520H and 520L are gate drivers. The pre-driver 520H drives the high-side transistor MH according to the control signal HG, and the pre-driver 520L drives the low-side transistor ML according to the control signal LG.
The above is the configuration of the driving circuit 500. Next, the operation thereof will be described.
Fig. 2 (a) and (b) are equivalent circuit diagrams showing current paths of the driving circuit 500 in the 1 st period T1 and the 2 nd period T2 of the driving circuit 500 in fig. 1. As shown in fig. 2 (a), in the short-circuit time T1, since the high-side transistor MH and the low-side transistor ML are simultaneously turned on, an input voltage V is applied between both ends of the series connection circuit of the inductors L1 and L2 H . For easy understanding, if it is assumed that the on-resistance of the high-side transistor MH and the low-side transistor ML is zero, the current I SHORT Flows from the input terminal IN to the ground terminal GND via the inductors L1 and L2. Current I SHORT Expressed by equation (1), increases with time at a constant slope.
I SHORT ＝1/(L1+L2)×∫V H dt＝V H /(L1+L2)×t…(1)
Magnetic energy E1 and E2 is stored in the inductors L1 and L2, respectively.
E1＝1/2·L1×I SHORT 2
E2＝1/2·L2×I SHORT 2
As shown in fig. 2 (b), in the light emission period T2, since the low-side transistor ML is turned off, a high-side current I flows through the inductor L1 and the high-side transistor MH L1 Is supplied to the light emitting element 402 via the inductor L3. In addition, in the light emission period T2, a current I flowing through the inductor L2 L2 Is not zero, but I DRV ＝I L3 ＝I L1 －I L2 . Positive coil current I L2 Drain capacitance flowing into low side transistor, negative coil current I L2 Flows from the ground terminal to the switching node via the body diode of the low-side transistor ML.
Fig. 3 is an operation waveform diagram of the driving circuit 500 of fig. 1. The high level (H) and the low level (L) of the control signals HG and LG correspond to on and off, respectively.
At time t 0 Previously, the control signal HG was L, LG H, the high-side transistor MH was turned off and the low-side transistor ML was turned on. A drive voltage V of 0V is supplied to the cathode of the light emitting element 402 DRV 。
At time t 0 The light emission command S1 is at a high level (H). The control circuit 530 changes the control signal HG to H in response to the assertion of the light-emitting command S1. Thereby, to the short-circuit time T1, both the high-side transistor MH and the low-side transistor ML are turned on.
At time T after passage of period T1 of time 1 1 The control circuit 530 changes the control signal LG to L. Thereby, the low-side transistor ML is turned off, and the light emission period T2 in which only the high-side transistor MH is turned on is shifted.
At time t 1 When the low-side transistor ML is turned off, the magnetic energy accumulated in the inductors L1 and L2 drives the voltage V DRV And rises sharply. Thereby, the driving current I flowing through the light emitting element 402 DRV And also rises sharply.
At time t 2 When the light emission command S1 is at the low level (L), the control signal HG is at the low level, the high-side transistor MH is turned off, and the process shifts to the 3 rd period (dead time) T3. At the next time t 3 The control signal LG is at a high level, and transitions to a 4 th period (standby period) T4.
Next, simulation results of the driving circuit 500 according to the embodiment will be described. Fig. 4 is a circuit diagram of a calculation circuit model of the driving circuit 500 used in the simulation. Inductors L1 to L3 were 0.2nH. Cj is the junction capacitance of the light emitting element 402, and the capacitance value thereof is 10pF. The pre-driver 520H includes a gate resistor (charging resistor) R1 for conduction and a schottky diode SD1 for turn-off. Similarly, the pre-driver 520L includes a gate resistor R2 for conduction and a schottky diode SD2 for turn-off. The resistance of the gate resistors R1 and R2 is 510mΩ.
Fig. 5 (a) is a waveform diagram of control signals of the driving circuit 500 according to the embodiment. The control signals HG and LG are respectively expressed with reference to the source voltages of the high-side transistor MH and the low-side transistor ML. The length of the light emission period T2 is 10ns, and the length of the short-circuit time T1 is 2ns.
Fig. 5 (b) is a waveform diagram of a control signal of the drive circuit of comparative technique 1. In comparative technique 1, dead time T3 is inserted in the same manner as in the conventional inverter control. The dead time here has a length of 1ns. The length of the light emitting device T2 is 10ns.
Fig. 6 (a) and (b) are waveform diagrams showing voltages and currents generated at a plurality of nodes of the driving circuit 500 according to the embodiment. Waveforms of voltages V (a) -V (e) at nodes a-e of fig. 3 are shown in fig. 6 (a), and currents I of inductors L1-L3 are shown in fig. 6 (b) L1 、I L2 、I L3 Drive current I DRV 。
Referring to voltage V (a) of node a shown in fig. 6 (a), the voltage exceeds input voltage V generated by power supply circuit 404 H =25v and jumps to around 37V. The voltages V (b) and V (c) at the nodes b and c also jump up to around 50V. Therefore, the withstand voltage and the input voltage V of the high-side transistor MH and the low-side transistor ML H To the same extent is insufficient, can be the input voltage V H More preferably 2.5 times or more, and still more preferably 3 times or more.
FIG. 7 shows the driving current I according to the embodiment DRV And comparing the drive current I of technique 1 DRV Is a waveform diagram of (a). The solid line is the driving current I based on the control signal shown in FIG. 5 (a), which is an embodiment DRV The dotted line is the drive current I based on the control signal shown in comparative technique 1, fig. 5 (b) DRV 。
In comparative technique 1, the drive current I DRV Unlike the rise rate (slew rate) of 19.1 kA/. Mu.s, in the present embodiment, the drive current I DRV The rise rate (slew rate) of (i) was 62.3 kA/. Mu.s, which was found to be about 3 times. That is, according to the present embodiment, when the pulse width is long to some extent (for example, when 10ns or more), the current waveform can be made to approximate a rectangular wave shape.
Next, other advantages of the driving circuit 500 of the embodiment will be described by comparison with the related art (hereinafter, referred to as a comparison technique 2) disclosed in the comparison technique 1 and the patent document 3. In the comparative technique 2, a capacitor that is charged before light emission is provided. The light emitting element and the switch are connected between both ends of the capacitor, and the charge charged in the capacitor flows as a driving current to the light emitting element when the switch is turned on. The method of comparative technique 2 is referred to as a capacitor discharging method.
FIG. 8 shows the driving current I according to the embodiment DRV1 (solid line) and comparative technique 1 DRV2 (dotted line) drive current I of comparative technique 2 DRV3 Waveform diagram (one-dot chain line). Here, a Gaussian waveform driving current I with a pulse width of 2ns is generated DRV As a target. Input voltage V of the embodiment H 25V, drive current I DRV1 The peak value of (2) is 54A and the pulse width is 2ns.
In comparative technique 3 (capacitor discharge type), parasitic inductance of each component affects, and it is difficult to generate a gaussian waveform having a pulse width of 2ns.
To obtain the same degree of driving current I as in the embodiment DRV In comparison technique 1, an input voltage V of 75V is required for the peak value (55A) H . In comparative technique 2, an input voltage (capacitor voltage) of 550V is required. That is, according to the present embodiment, the required input voltage V can be made H The voltage level of (2) is reduced by about 1/3 times as compared with comparative technique 1 and about 1/22 times as compared with comparative technique 2.
FIG. 9 (a) shows the coil current I L1 ～I L3 And drive current I DRV Fig. 9 (b) is a diagram showing the dependence of the short-circuit time T2 on the length of the driving voltage V DRV A graph of dependence on the length of the short-circuit time T2. The short-circuit time T2 varies between 0 and 5ns in 1ns steps. The longer the short-circuit time T2 is, the more the magnetic energy stored in the coils L1 and L2 increases during the short-circuit time, so that the driving voltage V can be set DRV And drive current I DRV The rising slew rate of (c) increases.
Next, noise countermeasures will be described. As shown in fig. 6 (a), the voltage V (a) at node a of fig. 3 greatly exceeds the voltage V (V) generated by the power supply circuit 404Current voltage V H And vibrates. When the vibration is input to the power supply circuit 404, the voltage withstand of the output smoothing capacitor of the power supply circuit 404 may be exceeded, and other circuits may be adversely affected.
Fig. 10 is a circuit diagram of a part of a driving circuit 500a of modification 1. The driver circuit 500a includes ferrite beads 540 and feed-through capacitors 542. Ferrite bead 540 is provided between output node 405 of power supply circuit 404 and high-side transistor MH. IN addition, a feed-through capacitor 542 is connected between the input terminal IN of the driving circuit 500 and the ground terminal.
With this configuration, noise due to the voltage vibration generated at the node a can be cut off, and adverse effects on the power supply circuit 404 can be prevented.
The feed-through capacitor 542 may be omitted and only the ferrite bead 540 may be provided, or the feed-through capacitor 542 may be omitted and only the ferrite bead 540 may be provided.
(use)
Fig. 11 is a block diagram of an active sensor 70 of an embodiment. The active sensor 70 is a gated camera, a ToF camera, a LIDAR, or the like, including a light emitting device 72, a light sensor 74, and a controller 76.
The light emitting device 72 emits light by a plurality of pulses at the time of 1-time sensing, and irradiates the field of view with pulsed illumination light. The light emitting device 72 includes the light emitting device 400 of fig. 1.
The light L1 emitted from the light emitting device 72 is reflected by the object OBJ and enters the photosensor 74. The reflected light L2 is delayed by τ with respect to the outgoing light L1.τ corresponds to a distance z from the object OBJ and is expressed by formula (1). Let τ be the round trip time of the light.
τ＝2×z/c…(1)
c represents the speed of light.
The photosensor 74 controls exposure timing and exposure time so that each pulse contained in the reflected light L1 can be detected in synchronization therewith at each light emission of the light emitting device 72. The light emission timing of the light emitting device 72 and the exposure timing of the light sensor 74 are controlled by a controller 76. The light sensor 74 may be a single-pixel detector or an image sensor.
The reflected light L2 from the object is incident on the light sensor 74 a plurality of times in accordance with the plurality of light emissions of the light emitting device 72. The light sensor 74 integrates the reflected light received a plurality of times, and outputs a signal corresponding to the integrated value.
The purpose of the active sensor 70 is described next. One embodiment of the active sensor 70 is a gated camera.
Fig. 12 is a block diagram of a gating camera 20 of an embodiment. The gating camera 20 divides the depth direction into a plurality of N (N.gtoreq.2) ranges RNG 1 ～RNG N And shooting is performed.
The gating camera 20 includes an illumination device 22, an image sensor 24, a controller 26, and an image processing section 28. The illumination device 22 corresponds to the light emitting device 72 of fig. 11, the image sensor 24 corresponds to the light sensor 74 of fig. 11, and the controller 26 corresponds to the controller 76 of fig. 11.
The illumination device 22 irradiates illumination light L1 including a plurality of pulses to the field of view in synchronization with the light emission timing signal S1 supplied from the controller 26. The illumination light L1 is preferably infrared light, but not limited thereto, and may be visible light having a predetermined wavelength.
The image sensor 24 is configured to be capable of performing exposure control in synchronization with the photographing timing signal S2 supplied from the controller 26, and is configured to be capable of generating a slice image IMG. The image sensor 24 has sensitivity to the same wavelength as the illumination light L1, and captures reflected light (return light) L2 reflected by the object OBJ.
The controller 26 holds the light projecting timing and the exposure timing predetermined for each range RNG. The controller 26 photographs a certain range RNG i At this time, the light emission timing signal S1 and the photographing timing signal S2 are generated based on the light emission timing and the exposure timing corresponding to the range, and photographing is performed. Gating camera 20 is capable of generating and multiple ranges RNG 1 ～RNG N Corresponding plurality of slice images IMG 1 ～IMG N . In the ith slice image IMG i In (1) shooting a corresponding range RNG i An object contained in the container.
Fig. 13 is a diagram illustrating the operation of the gating camera 20 of fig. 12. In FIG. 13, the range RNG for the ith range is shown i When the measurement is performedIs a state of (2). The illumination device 22 is synchronized with the emission timing signal S1 at time t 0 ～t 1 The light-emitting period tau therebetween 1 Is illuminated during the period of (2). At the top, a graph of light rays is shown with the horizontal axis representing time and the vertical axis representing distance. Will range from gating camera 20 to range RNG i The distance of the boundary of the front of the frame is d MINi Will reach the range RNG i The distance of the boundary on the deep side is d MAXi 。
Distance d of arrival of light emitted from illumination device 22 at a certain point in time MINi While the round trip time T until the reflected light returns to the image sensor 24 MINi Is T MINi ＝2×d MINi And/c. c is the speed of light.
Also, the light emitted from the illumination device 22 reaches the distance d at a certain time MAXi While the round trip time T until the reflected light returns to the image sensor 24 MAXi Is T MAXi ＝2×d MAXi /c。
In the range of want to i When the object OBJ included in the image is captured, the controller 26 controls the image capturing device to capture the image at time t 2 ＝t 0 +T MINi Exposure is started at time t 3 ＝t 1 +T MAXi The exposure is ended to generate a shooting timing signal S2. This is 1 exposure action.
RNG in the i-th range of photographing i In this case, light emission and exposure are repeated a plurality of times, and the measurement result is accumulated in the image sensor 24.
Fig. 14 (a) and (b) are diagrams illustrating images obtained by the gating camera 20. In the example of FIG. 14 (a), in-range RNG 1 In the presence of objects (pedestrians) OBJ 1 In the range RNG 3 In which there is an object (vehicle) OBJ 3 . Fig. 14 (b) shows a plurality of slice images IMG obtained in the state of fig. 14 (a) 1 ～IMG 3 . In the process of shooting slice images IMG 1 At this time, since the image sensor passes only through the RNG from the range 1 Is exposed to light reflected thereby in the slice image IMG 1 In shot pedestrian OBJ 1 Object image OBJ of (a) 1 。
In the process of shooting slice images IMG 2 At this time, since the image sensor passes only through the RNG from the range 2 Is exposed to light reflected thereby in the slice image IMG 2 No object image is captured.
Also, in capturing slice images IMG 3 At this time, since the image sensor passes only through the RNG from the range 3 Is exposed to light reflected thereby in the slice image IMG 3 In which only the object image OBJ is shot 3 . As described above, according to the gating camera 20, the object can be photographed separately for each range.
The above is the action of the gating camera 20. In this gate camera, by making the time of light emission of the illumination device 22 uneven, the image of the surrounding pulse light source can be reduced, and a clear image with less noise component can be obtained.
Fig. 15 is a diagram showing a vehicle lamp 200 incorporating the active sensor 70. The vehicle lamp 200 includes a housing 210, an outer lens 220, a high beam and low beam lamp unit 230H/230L, and an active sensor 70. The lamp unit 230H/230L and the active sensor 70 are housed in the case 210.
A part of the active sensor 70, for example, the optical sensor 74 may be provided outside the vehicle lamp 200, for example, on the back side of the indoor mirror.
Fig. 16 is a block diagram showing a vehicle lamp 200 including the object recognition system 10. The vehicle lamp 200 and the vehicle ECU304 together form a lamp system 310. The vehicle lamp 200 includes a light source 202, a lighting circuit 204, and an optical system 206. Further, the vehicle lamp 200 is provided with the object recognition system 10. The object recognition system 10 includes an active sensor 70 and an arithmetic processing device 40.
The arithmetic processing device 40 is configured to be able to identify the kind of the object based on the image obtained by the active sensor 70. The arithmetic processing device 40 includes a classifier implemented based on a prediction model generated by machine learning. The algorithm of the classifier is not particularly limited, and YOLO (You Only Look Once: look only once), SSD (Single Shot MultiBox Detector: single click multi-frame detector), R-CNN (Region-based Convolutional Neural Network: area-based convolutional neural network), SPPnet (Spatial Pyramid Pooling: spatial pyramid pooling), fast R-CNN, DSSD (Deconvolution-SSD), mask R-CNN, or the like may be employed, or algorithms developed in the future may be employed.
The arithmetic processing device 40 can be realized by a combination of a processor (hardware) such as a CPU (Central Processing Unit: central processing unit) or MPU (Micro Processing Unit: micro processing unit), microcomputer, and the like, and a software program executed by the processor (hardware). The arithmetic processing device 40 may be a combination of a plurality of processors. Alternatively, the arithmetic processing device 40 may be configured by only hardware.
The information on the object OBJ detected by the arithmetic processing unit 40 may be used for controlling the light distribution of the vehicle lamp 200. Specifically, the lamp-side ECU208 generates an appropriate light distribution pattern based on the information related to the type and position of the object OBJ generated by the arithmetic processing unit 40. The lighting circuit 204 and the optical system 206 operate to obtain a light distribution pattern generated by the luminaire-side ECU 208.
Information on the object OBJ detected by the arithmetic processing unit 40 may be transmitted to the vehicle-side ECU304. The vehicle-side ECU may also perform automatic driving based on the information.
It should be understood by those skilled in the art that the embodiments are merely examples, and various modifications exist to the combination of the respective constituent elements and the respective processes, and such modifications are also included in the present disclosure or the scope of the present invention.
[ Industrial availability ]
The present disclosure relates to a driving circuit of a light emitting element.
[ description of reference numerals ]
10 … object recognition system, OBJ … object, 20 … gate camera, 22 … lighting device, 24 … image sensor, 26 … controller, S1 … lighting timing signal, S2 … shooting timing signal, 40 … operation processing device, 70 … active sensor, 72 … lighting device, 74 … photosensor, 76 … controller, 200 … vehicle light fixture, 202 … light source, 204 … lighting circuit, 206 … optical system, 310 … light fixture system, 304 … vehicle side ECU,400 … lighting device, 402 … lighting element, 500 … driving circuit, 510 … half bridge circuit, MH … high side transistor, ML … low side transistor, 520 … pre-driver, 530 … control circuit.
Claims (10)
1. A driver circuit for a semiconductor light emitting element, comprising:
an input terminal for receiving an input voltage of a direct current,
an output terminal connected to the semiconductor light emitting element,
a half-bridge circuit including a high-side transistor provided between a switching node connected to the output terminal and the input terminal and a low-side transistor provided between the switching node and a ground terminal, and
and a control circuit that turns on both the high-side transistor and the low-side transistor in a period 1 according to a light emission instruction of the semiconductor light emitting element, and turns on the high-side transistor and turns off the low-side transistor in a period 2.
2. The driving circuit according to claim 1, wherein,
the withstand voltage of the high-side transistor and the low-side transistor is 2.5 times or more the input voltage.
3. A driving circuit according to claim 1 or 2, wherein,
the high-side transistor and the low-side transistor are GaN-FETs (Field-Effect Transistor: field effect transistors).
4. A driving circuit according to any one of claims 1 to 3, wherein,
the length of the wiring pattern reaching the switching node from the input terminal via the high-side transistor is longer than 100 μm.
5. A driving circuit according to any one of claims 1 to 3, wherein,
the length of the wiring pattern reaching the switching node from the ground terminal via the low-side transistor is longer than 100 μm.
6. A driving circuit according to any one of claims 1 to 5, wherein,
the ferrite bead is arranged between an output node of the power supply circuit generating the input voltage and the input terminal.
7. A driving circuit according to any one of claims 1 to 6, wherein,
a feed-through capacitor is also included in connection with the input terminal.
8. A driving circuit according to any one of claims 1 to 7, wherein,
the control circuit turns off the high-side transistor and the low-side transistor during a period of a 3 rd period after the 2 nd period.
9. An active sensor, comprising:
light emitting device for irradiating field of view with pulsed illumination light
A photosensor that receives reflected light of the pulsed illumination light from the field of view;
the light emitting device includes:
semiconductor light emitting device
The driving circuit according to any one of claims 1 to 8 which drives the semiconductor light-emitting element.
10. An object recognition system, comprising:
an active sensor as claimed in claim 9, and
an arithmetic processing device capable of recognizing the kind of the object based on the image obtained by the active sensor.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2021-139663 | 2021-08-30 | ||
| JP2021139663 | 2021-08-30 | ||
| PCT/JP2022/032433 WO2023032922A1 (en) | 2021-08-30 | 2022-08-29 | Drive circuit for light-emitting element, active sensor, and object identification system |
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| Publication Number | Publication Date |
|---|---|
| CN117897631A true CN117897631A (en) | 2024-04-16 |
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| CN202280058792.0A Pending CN117897631A (en) | 2021-08-30 | 2022-08-29 | Light emitting element driving circuit, active sensor, and object recognition system |
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| Country | Link |
|---|---|
| JP (1) | JPWO2023032922A1 (en) |
| CN (1) | CN117897631A (en) |
| WO (1) | WO2023032922A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0659038A (en) * | 1992-08-07 | 1994-03-04 | Nissan Motor Co Ltd | Laser radar for vehicle |
| JP6413960B2 (en) * | 2015-07-08 | 2018-10-31 | 株式会社デンソー | Distance measuring device |
| IL257786B2 (en) * | 2018-02-28 | 2023-04-01 | B G Negev Technologies & Applications Ltd At Ben Gurion Univ | Low voltage sub-nanosecond pulsed current driver ic for high-resolution lidar applications |
| DE102018108910B3 (en) * | 2018-04-16 | 2019-07-04 | Elmos Semiconductor Aktiengesellschaft | Light source for short LED light pulses and method for generating light pulses |
| JP7354717B2 (en) * | 2018-11-30 | 2023-10-03 | 株式会社リコー | Drive circuit, light emitting device, distance measuring device, and moving object |
| US20210111533A1 (en) * | 2019-03-01 | 2021-04-15 | Gan Systems Inc. | Fast pulse, high current laser drivers |
| CN210246596U (en) * | 2019-09-04 | 2020-04-03 | 中山联合光电科技股份有限公司 | Laser diode power supply |
| US11545811B2 (en) * | 2019-10-02 | 2023-01-03 | Analog Devices International Unlimited Company | Laser driver designs to reduce or eliminate fault laser firing |
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2022
- 2022-08-29 JP JP2023545563A patent/JPWO2023032922A1/ja active Pending
- 2022-08-29 CN CN202280058792.0A patent/CN117897631A/en active Pending
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| JPWO2023032922A1 (en) | 2023-03-09 |
| WO2023032922A1 (en) | 2023-03-09 |
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